Overload circuit breaker



Feb. 23, 1960 E. v. suNDT ovERLoAD CIRCUIT BREAKER Filed March 15, 1957 al1 5:4 [53 A I `l) @mll'l'mlullfl' hf Il" @www "WW 1N VEN TOR. ///ard Ma/m? United States PatentO 2,926,227l ovERLoAD CIRCUIT BREAKER Edward v. Smidt, Wiimeae, In. Application March 15, 1957, Serial No. 646,445 1'4 claims. (ci. 20o-ss) The principal object of this invention is to provide an improved overload circuit breaker for protecting an electric circuit against current overload conditions therein, wherein the circuit breaker opens the electric circuit only after a time interval where sustained low current overload conditions occur and wherein the circuit breaker immediately opens the electric circuit whereV sudden high current overload conditions occur.

In circuit breakers of the thermal bimetal snap action type, substantial time lag characteristics are obtainable for sustained low overload conditions since the bimetallic element must heat to the point where stress energies are built up sufficiently to make the element snap the breaker open. However, on severe overload conditions, the bimetallic type circuit breakers can burn up before this snap is able to take place. The circuit breaker of this invention, which is also of the thermal type, has the desirable time lag characteristics of the bimetallic snap action type, but since it is not of the type requiring snapping of the thermal element to open the breaker, it may operate more quickly and burning up of the circuit breaker due to severe overload conditions is substantially prevented.

Circuit breakers of the magnetic type have the disadvantage of tripping open on short peak overloads and, where provision for time lag is incorporated therein, considerable cost is added thereto. In the circuit breaker of this invention, a rapid magnetic opening of the circuit breaker is provided upon a short circuit, a sudden high current overload condition, and yet time delay is provided for opening the circuit breaker under sustained low current overload conditions. Thus, the circuit breaker of this invention incorporates the favorable characteristics found in thermal bimetal types and magnetic types of circuit breakers, but eliminates the unfavorable characteristics thereof.

Briey, the overload circuit breaker of this invention for protecting an electric circuit against current overload conditions includes high current coil means, circuit controlling contact means and an armature connected in series in the electric circuit to be protected. The armature actuates the contact means, and has a resistanceto current ow so as to be heated by thepassage of current therethrough, and has high magnetic permeability below and a low magnetic permeability above'a predetermined Curie point temperature. A permanent magnet is magnetically coupled -to the armature and acts upon the armature in a direction to hold the contact means closed when the temperature of the armature is below the Curie point temperature. Spring means act upon the armature in avdirection touncouple the armature from the magnet and open the contact means when the temperature of the armature-rises to substantially the Curie point temperature -due to `a sustained low current overload condition in the electric circuit to be protected for opening the circuit. The time lag here provided is determined by the time required to heat the armature to substantially the Curie point temperature and when this occurs the poses of mounting the overload circuit breaker.

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circuit breaker automatically opens without the necessity for building up stresses in the armature as is required in the case of bimetallic snap acting elements. Burning up of the circuit breaker on severe current overload conditions is greatly minimized if not absolutely prevented.

To protect absolutely the circuit breaker against short circuit conditions, i.e., sudden high current overload conditions, core means having high magnetic permeability are also carried by the armature and are associated with the series connected high current coil means for moving the armature in said opposite direction to uncouple the armature from the magnet and open the contact means when the current flow in the coil means exceeds a predetermined value due to a sudden high current overload condition in the electric circuit to be protected for opening said circuit. Thus, rapid magnetic opening of the circuit breaker is provided upon the occurrence of short circuit conidtions while time delay opening is provided for sustained low current overload conditions, this being simply and inexpensively accomplished and without danger of burning up of the circuit breaker.

The circuit breaker of this invention also includes means for manually resetting the circuit breaker after it has opened the electric circuit. This is accomplished by manually moving the permanent magnet to magnetically recouple the armature to the magnet after the armature has been moved by the spring means or the high current coil means to open the contact means. In this way `the contact means may be reclosed and the circuit breaker reset. The circuit breaker is at all times trip free, even during the manual resetting thereof, so that circuit protection is at all times afforded.

Further objects of this invention reside in the details of construction of the circuit breaker and in the cooperative relationships between the component parts thereof.

Other objects and advantages of this invention will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawing, in which:

Fig. I is a top plan view of the overload circuit breaker of this invention;

substantially A the terminal strip of Fig. 5 is folded upon itself.

Referring first to Figs. 1 to 4, the overload circuit breaker of this invention is generally designated at 10. It includes a base 11 formed of electrical insulating ma- -terial such as Bakelite or the like. The base 11 is provided at its ends with slots 12 which are utilized for pur- The base 11 is centrally provided with a raised portion 13 frornwhich extend ribs 14 forming cavities 15 on each side of the raised portion 13. The raised portion 13 adjacent each cavity 15 is provided with a notch 16, and the floors of the cavities 15 are each provided with a hole 17. The raised portion 13 is provided with a pair of diagonally arranged holes 18, and a pair of diagonally arranged bosses 19.

A terminal strip is designated at 20 in Fig. 5 and this terminal strip may be for-med from any suitable electrically conductive metal such as brass or the like. This terminal strip 2i) is provided with a pair of notches 21 which open on one side edge of the strip, and a pair of notches 22 which open on the other side edge thereof.

As shown, these notches are preferably of keyhole configuration. Between two of the notches 21 and 22, the strip 20 is provided with a U-shaped slit 23 to form a tongue 24. One end of the terminal lstrip 2G is provided with a hole 25, and the other end is provided with a tapped hole 26. The terminal strip 2t? is folded upon itseif as indicated in Fig. 6, wi-th `the notches 21 and 22 in alignment. This folding forms a high current coil 27 having a cent-ral hole 28 formed by the notches 21 and 22. In the folding operation, the tongue 24- is also formed. The end of the terminal strip is bent upwardly at 29 to form an ear for making electrical connection by means of a screw 32 received in the tapped hole 216. The other end of the terminal strip 29 is bent -as indicated at 30 to form a contact support for carrying a stationary contact 31, which is secured in the hole 25.

Two of these coil and Contact support members are preferably utilized in the overload circuit breaker and they are arranged in the cavities 15 of the base 11. When they are so arranged, they are held in position oy the ribs 14 on the base and by the tongues 24 extending in-to the slots 16. The central holes 28 in ythe coils 27 overlie the holes 17 in the cavities 15, and the stationary contacts 31 preferably overlie the holes 28 in the coils 27. An insulating sleeve 34, which may be formed from Flamino-l insulating sleevingV material, is inserted in the hole 28 of each coil '27 for core insulating puposes. These sleeves 34 also extend into the holes 17 in the cavities 15 further to assist in maintaining the coils 27 in proper position on the base 11.

resiliently urging the pin 51 downwardly with respect to the carrier 44 and the magnet -49 carried thereby.

Located Vwithin the cover 36 is an electrically conductive armature 56 wl ich has a resistance to current ow so as to be heated by the passage of current therethrough and which has high magnetic permeability `below and low magnetic permeability above a predetermined Curie point temperature. This armature is preferably formed from a ferrous nickel -alloy having a Curie point temperature of substantially 350 degree-s Fahrenheit. The ends of the armature 56 carry movable contactsxl and soft iron magnet rivets 58, the contacts and rivets being suitably secured to the armature as by welding or the like. The rivets 58 carry cores 59 formed from Armco iron or the like, these cores 59 extending into the insulating core sleeves 28.

The armature 56 is adapted to be raised and lowered, and it is held in its raised position by the permanent magnet 49 with the movable contacts 57 engaging the The overload circuit breaker of this invention also Y includes a cover 36 having la top wall 37, side walls 38, which engage the centr-al raised portion 13 and the ribs 14 of the base, and end walls 39 which extend downwardly between the ribs 1'4 and which engage the terminal strips to hold the same securely in place. The cover is secured to the base by means of a pai-r of rivets 41 extending through holes in the top wall 37 of the cover and through the holes 18 in the base. The top wall 37 of the cover is also centrally provided with an upwardly extending sleeve 40. The corners of the cover, where the top wall and the end walls meet, are provided with projections 42 which engage the contact supporting extensions 30 further to assist in rigidly holding the folded terminal strips in place. The cover 36 may be made of any suitable electrical insulating material such yas Bakelite or the like.

Slidably mounted in the sleeve 40 of `the cover 36 is a carrier 44 having a cylindrical portion, a closed top, and an outwardly extending flange 45, the flange 45 being arranged within the cover and the closed top of the carrier extending outwardly from 4the sleeve 40 of the cover to form a push button.` The ange `45 of the carrier has two of its corners rounded off, 4as indicated at 46, so as to clear the rivets 41, 'and has two of its other corners provided with downwardly extending bosses 47. The carrier may be formed from any suitable electrical insulating material such as Bakelite or the like. The carrier is spring urged to its upper position where the ilange 45 engages the top wall 37 of the cover by means of a pair of springs 48 extending between the pair of bosses 19 on the base, and the pair of bosses 47 on the carrier. The carrier may be moved downwardly against the action of these springs 4S by manually pressing on the closed top thereof in the manner of pressing Ia push button. y

The carrier 44 internally carries a permanent magnet 49 having a pair of downwardly extending poles and the magnet may be an Alnico or the like magnet. The magnet 49 is provided with a vertically extending central hole Sil in which is Slidably mounted a pin 5,1 made of electrical insulating material `such as glass tiled Plaskon or the like. This pin Slis also Slidably mounted in `a sleeve portion 52 on the carrier 44. The pin 51 is provided with a flange 53, and a spring 54 is interposed between this ange and the closed top of the carrier for stationary contacts 31. When the overload circuit breaker is connected into the circuit to be protected lby means of the screws 32, a series circuit is completed through the coils 27, the stationary contacts '31, the movable contacts 57, yand the armature S6. Under normal load conditions, the armature 56 is held raised by the permarient magnet 49 with the movable contacts engaging the stationary contacts 'and the armature, having a resistance to current dow, is heated by the current ow therethrough in accordance with the `amount of the current flow. the circuit, the armature 56 will heat up to substantially the Curie point temperature, whereuponrthe magnetic permeability of the armature quickly and materially reduces. When this occurs, the spring 54 operates the pin 51 for forcibly moving the armtaure 56 away from the permanent magnet 49, and to separate the movable Y contacts 57 from the stationary contacts 31. As a result, the circuit to be protected is opened upon the occurrence of these sustained low overload conditions. Under low overload condtiions, 4the armature 56 loses its magnetic permeability at approximately percent of the calibrated rating of the circuit breaker, and when this overload condition occurs, the armature 56 is quickly pushed oil of the permanent magnet 49 Yby the pin 51, and is held inthe circuit opening position by the spring actuated pin S1.

IIn order to manually reset the circuit breaker, the carrier 44 is pushed downwardly against the action of the springs 48, to move the magnet 49 into engagement with the lowered armature 56. In so doing, the spring 5'4 is compressed, and the pin 51 retracted. lf, when this is done, the armature 56 has cooled below the Curie point temperature so as to obtain high magnetic permeability, the armature is -then magnetically recoupled to ythe magnet V49. Wehn the carrier is released, the springs y48 raise the same, and the magnet 49 moves the amature 55 upwardly to cause the movable contacts 57 to re-engage the stationary contacts 31. Itis thus seen that, in the manual resetting of the overload circuit breaker, trip free action is obtained during -the resetting openation, for if overload conditions Yshould occur, the anntaure would mediately be moved by the spring 54 to the open position.

Due to the fact that the coils 27 formed by the terminal strips 20 are extremely high current coils, there is no substantial action by these coils upon the cores 59 carried by the amature duringV low overload conditions. If, however, there should be a sudden high overload condition,

such as caused by a short circuit or the like, a large curl rent ,flow would pass through the coils 27', which would immediately operate to pull the cores 59 downwardly and pull the armature 56 away from the permanent magnet 49, thereby separating the movable contacts 57 from the stationary contacts 31 to open the circuit. In other words, the magnetic eld produced by the coils 27 is substantially negligible Vin normal operation with a cur-' Under a short circuit, how-r` rent. of 3.0 or 60 amper-es.

I-f there is a sustained overload condition in amaca?- ever, this current value may increase to 1,000 or 2,000

amperes in a few milliseconds, and the ampere turns thus provided by the high current coils 2.7 snap the circuit high overloadcondition, in the same way `as it is reset' following operation due to sustained low overload conditions, trip free resetting being obtained in both instances.

While for purposes of illustration, one form of this invention has been disclosed, other forms thereof may become apparent to those skilled in the art upon reference to this disclosure and, therefore, this invention Vis to be limited only by the scope of the appended claims.

. I claim as my invention:

l. A manually resettable overload circuit breaker for protecting an electric circuit against current overload conditions therein comprising, stationary contact means for connection into the electric circuit to be protected, an electrically conductive armature having resistance to current ow so as to be heated by current iow therethrough and high magnetic permeability below and low magnetic permeability above a predetermined Curie point temperature, movable contact means carried by the armature and adapted to engage the stationary contact means for connecting the armature in series with the electric circuit to be protected to heat the armature in accordance with the current flow in said electric circuit, a permanent magnet acting upon the armature -in a direction to hold the movable contact means in engagement-with the stationary contact means when the temperature of the armature is below the Curie point temperature, andk spring means acting upon the armature in the opposite direction tov disengage the movable contact means from the stationary contact means when the temperature ofthe armature rises to substantially the -Curie point temperature due to a' current overload condition in the electric circuit to be protected for opening said circuit, and a manually operated resiliently urged mounting means for the permanent magnet for normally maintaining the magnet in one position magnetically to maintain the armature in a position to hold the movable contact means in engagement with the stationary contact means, and for manually moving the magnet to another position 4to magnetically couple the armature to the magnet after the armaure has been magnetically uncoupled from the magnet and moved by the spring means to a position where the movable contact means is disengaged from the stationary contact means for the purpose of manually resetting the circuit breaker. v

2. A manually resettable overload circuit breaker for protecting an electric circuit against current overload conditions therein comprising, aY pair of spaced apart stationary contacts for series connection into the electric circuit to be protected, an electrically conductive armature having resistance to current ow so as to be heated by current ow therethrough and high magnetic permeability below and low magnetic permeability above a predetermined Curie point temperature,va pair of movable con-` tacts carried by the armature and adapted torengage the pair of stationary contacts for connecting the armature in series with the electric circuit to be protected to heat the armature in accordance with the current ow in' said electric circuit, a permanent magnet acting upon the armature between the movable contacts in a direction to hold the movable contacts in engagement with the stationary contacts when the temperature of the armature is below the Curie point temperature, and spring means acting upon the armature between the movable contacts in the opposite direction to disengage the movable contacts from the stationary contacts when the temperature ofthe armature rises to substantially the Curie point temperature due to a current .overload condition in the electric circuit to be protected for opening said circuit, and a manually 'operated resiliently urged mounting meansv for the permanent magnet for lnormally maintaining the magnet in one position magnetically to maintain the armature in a position to hold the pair of movable contacts in engagement with the pair of stationary contacts, and for manually moving the magnet to another position tomagnetically couple the armature to the magnet after the armature has been magnetically uncoupled from the magnet and moved by the spring means to a position where the pair of movable contacts is disengaged from the pair of stationary contacts for the purpose of manually resetting the circuit breaker.4

3. A manually resettable overload circuit breaker for protecting an electric circuit against current overload conditions therein comprising, stationary contact means for connection into the electriccircuit to be protected, an electrically conductive armature having resistance to current ow so as to'be heated by current tlow therethrough and high magnetic permeability below and low magnetic permeability above a predetermined Curie point temperature, movable contact means carried by the armature and adapted to engage the stationary contact means for' the current-flow in said electric circuit, a manually op erated carrier mounted for movement between two positions, first spring means for moving the carrier to one of the positions and allowing manual movement of'the carrier to the other position, a permanent magnet carried by the carrier and acting upon the armature in a direction to hold the movable contact means in engagement with the stationary contact means when the carrier is in said one position and the temperature of the armature is below the Curie point temperature, second spring means acting upon the armature in the opposite direction to move the armature and disengage the movable contact means from the stationary contact means when the temperature ofthe armature rises to substantially the Curie point temperature due to a current overload condition inv the electric circuit to be protected for opening said circuit, said carrier being manually movable to said other position against the action of said first spring means to magnetically recouple the armature to the magnet after the armature has been moved by the second spring means and the armatu-re has cooled below the Curie point temperature, and said first spring means moving the carrier to said one position to move the magnetically recoupled armatureand hence to engagethe movable contact means with the stationary contact means for resetting the circuit breaker.

4. A manually resettable overload circuit breaker for protecting an electric circuit against current overload conditions therein comprising, a pair of spaced apart stationary contacts for series connection into the electric circuit to be protected, an electrically conductive armature having resistance to current flow so as tobe heated by current flow therethrough and high magnetic permeability below andlow magnetic permeability above a predetermined Curie point temperature, a pair ofy movable contacts carriedfby the armature and adapted to engage the pair of stationary contacts for connecting the armature in series with the electric circuit to be protectedto heat the armaturein accordance'with the current flow in said electric circuit, a manually operated carrier mounted for movement between twol positions, iirst spring means for moving the carrier to one of the positions and allowing manual movement of the carrier to the other position, a permanent magnet carried by the carrier and acting upon the armature between the movable contacts in a direction to hold the pair of movable contacts when the carrier is in said one position and the temperature of the armature is below the Curie point temperature, second spring means acting upon the armature between the movable contacts in the opposite direction to move the armature and disengage the pair of movable contacts from the pair of stationary -'contacts when the tempera- Y ture of the armature risesto substantially the Curie point temperature due to-a current overload condition in the electric circuit vto be protected for opening said circuit',v

armature has beenmoved by the second spring means and the armature has cooled below the Curie point temperature, and Ysaid first spring means moving the carrier to said one position to move the magnetically recoupled armature and hence to engage the pair of stationary contacts Vfor resetting the circuit. breaker.

5. A manually resettable overloadl circuit breaker for protecting an electric circuit against current overload conditions therein comprising, stationary contact means for connecting` into thev electric circuit to be protected, an electrically conductive armature having resistance to current flow vso as to be heated by current ow therethrough and high magnetic permeability below and low magnetic permeability abovel a predetermined Curie point temperature, movable contact means carried by the armature and adapted to engage the stationary contact means for connecting the armature in series with the electric circuit to be protected to heat the armature in accordance with the current flow in said electric circuit, a manually operated carrier mounted for movement between two positions, spring means for moving hold the movable contact means in engagement with the I stationary contactmeans when the carrier is in said one position and the temperature of the armature is belowY the Curie point temperature, a pin extending through the hole. in the, magnet and engaging the armature, a spring interposed between the pin `and the carrier and acting upon the pin for moving the armature in the opposite direction to disengage the movable contact means from the stationary contact means when the temperature of the armature rises to substantially the Curie point temperature due to a current overload condition in the electric circuit to be protected for opening said circuitpsaid carrier being manually movable to said other position against the action of: the spring means to magnetically recouple the armature to the magnet after the armature has been moved by thespring and pin and the armature has cooled below lthe Curie pointtem erature, and said spring means moving the carrier to said one position to move the magnetically recoupled armature and hence to engage the movable contact means with the stationary contact means for resetting the circuit breaker.

6. A manually resettable overload circuit breaker for protecting an electric circuit against current overload conditions therein comprising, a pair of spaced apart stationary contacts for series connection into the electric circuit to be' protected, an electrically conductive armature having resistance to` current flow so as to be heated by current tiow therethrough and high magnetic permeability below and low magnetic permeability above a predetermined CurieY point temperature, apair of movable contacts carried by -thel armature and adapted to engage the pair of stationary contacts for connecting the armature in seriesy with the electric circuit to be protected to heat the armature in accordance with the current flow in said electric circuit, a manually operated carrier mountedy for movement between two positions, spring means for moving the carrier to one of the positions and allowing manual movementv of the4 carrier to thel other position,l a permanent magnethaving a hole therein and carrier by the carrier and acting upon the armature between themovable contacts in a directionV to hold the pairV of1 movablev contacts in engagement with the pair of stationary contactsrwhen the carrier is in said one,Vv position and the temperature. of the armature is fit) below the Curie point temperature, a pin extending'f through the hole in the magnet and engaging the arma-V ture between the movable contacts, a spring interposed between the pin and the carrier and acting upon the pink for movingrthe armature in the opposite direction tof disengage the pair of movable contacts from the pair' of stationaryrcontacts when the temperature of Vthe armature rises to substantially the Curie point temperature due to a current overload condition in the electric circuit to be protected for opening said circuit, said Vcarrier being' manually movable to said other position against the action of` the spring means to magnetically recouple the armature to the magnet after the armatureV has been moved'by the springand pin and the armature has cooled below the Curie point temperature, and said spring means moving the carrier to said one position to move the magnetically recoupled armature and hence to engage the pair of movable contacts with the pairV of:

tact supporting extension of the terminal strip, an electrically conductive armature, movable Contact means carvried by the armature and `adapted to engage the stationary contact meansfor connecting the armature in series with the electric circuit to be protected, means acting upon the armature in a direction to hold the movable contact means in engagement with the stationary contact means, andv a Vcore having high magnetic permeability carried by the armature'and extending into the central opening of the coil for moving the armature in the opposite direction to disengage the movable contact means from the stationary contact means when the current ow in the coil exceeds a predetermined value due to a current overload condition in the electric circuit to be protected for opening the circuit.

8. An overload circuit breaker for protecting an electric circuit againstY current overload conditions therein comprisingga pair of terminal strips for connection into the electric circuit to be protected and each having a plurality ofoppositely arranged notches therein and beingy folded upon itself with the notches in alignment and" ment with the pair of stationary contacts, and a pair of cores having high magnetic permeability carried by the armature and extending intothe central openings ofthe pair of coils for moving the armature in the opposite direction to disengage the pair of movable contacts fromV the pair of stationary contacts when the current iiow in the coils exceeds a predetermined value due to a current overload condition in thelelectric circuit to be protected for opening the circuit.

9. An overload circuit breaker for protecting an electric circuit against current` overload conditions therein comprising, stationary contact means for connection into the electric circuit to be protected, an electrically conductive armature having resistance to current flow so as to` be heated by current owtherethrough and high magf netic permeability below and low magnetic permeability above ya predetermined Curie point temperature, movable contact means carried by the armature and adapted' to 9v engagethe stationary contact means for connecting the armature in series with the electric circuit to be protected to heat the armature in accordance with the current ow in said electric circuit, a permanent magnet acting upon the amature in a direction to hold the movable contact means in engagement with the stationary contact means hen the temperature of the armature is below the Curie point temperature, and spring means acting upon the armature in the opposite direction to disengage the movable vcontact means from the stationary contact means when the temperature of the armature rises to substantiallyv the Curie point temperature due to -a sustained low current overload condition in the electric circuit to 'be protected for opening said circuit, coil means connected in series with the stationary contact means, and core means having high magnetic permeability carried by the armature and extending'into the coil means for moving the -armature'in said opposite direction to uncouple the armature from the permanent magnet and disengage the movable contact means from the stationary contact means when the current ow in the coil means exceeds a pre determined value due to a sudden high current overload condition in the electric circuit to be protected for open ing said circuit.

10. An overload circuit breaker for protecting an electijic circuit against current overload conditions therein comprising, apair of spacedapart stationary contactslfor series connection into the electric circuit to be protected, an electrically conductive armature having resistance to current flow so as to be heated by current ow therethrough and 'high magnetic permeability below and low magnetic permeability above a predetermined Curie point temperature, a pair of movable contacts carried by the armature andadapted to engage the pair of stationary contacts for connecting the armature in series withthe electric circuit to be protected to heat the armature in accordance with the current ow in said electric circuit, a permanent magnet acting upon the armature between the movable contacts in a direction to hold the movable contacts in engagement with the stationary contacts when the temperature of the armature is below the Curie point temperature, land spring means acting upon the armature between the movable contacts in the opposite direction to disengage the movable contacts from the stationary contacts when the temperature of the armature rises to substantially -the Curie point temperature due to a sustained low current overload condition in the electricrfcircuit to be protected for opening said circuit, a pair of coils connected in series with the pair of stationary contacts, and a pair of cores having high magnetic permeability carried by the armature and extending intothe pair of coils for moving the armature in said opposite direction to uncouple the armature from the permanent magnet and disengage the movable contacts fromthe stationary contacts when the current ow in the pair'of coils exceeds a predetermined value due to a suddenhigh current overload condition inthe electric circuit to be pr'otected for opening said circuit.

l1. An overload circuit breaker for protecting an electric circuit against current overload conditions therein comprising, a terminal strip for connection into the electric circuit to be protected and having a plurality of oppositely arranged notches therein and being folded upon itself with the notches in alignment and forming a coll with a central opening and having a contact supporting extension, stationary contact means carried by the contact supporting extension of the terminal strip, an electrically conductive armature having resistance to current ow so as to be heated by current tiow therethrough and high magnetic permeability below and low magnetic permeability above a predetermined Curie point temperature, movable contact means carried by the armature and adapted to engage the stationary contact means for connecting the armature in series with the electric circuit to be protected to heat the armature in accordance with the lcurrent flow in said electric circuit, a permanent mag`.

contact means when the temperature of the armature.

rises to substantially the Curie point temperature due to a sustained low current overload condition in the electric circuit to be protected for opening said circuit, and a core. having` high magnetic permeability carried by the arma-v ture and extending into the central opening of the coil for movin-g the armature in the opposite direction to dis-iy engage the movable contact means from the stationary contact means when the current iiow in the coil exceeds a predetermined value due to a sudden high current over-I load condition in the electric circuit to be protected forA opening said circuit. l

12. An overload circuit breaker for protecting an electric circuit against current overload conditions therein comprising, a pair of terminal strips for connection intoV the electric circuit to be protected and each having a plurality of oppositely arranged notches therein and being folded upon itself with the notches in alignmentand forming a coil with a cent1-al opening and having a contact supporting extension, a pair of stationary contacts' carried respectively by the contact supporting extensions of the terminal strips, an electrically conductive armature having resistance to current ow so as to be heated by current flow therethrough and high magnetic permeability below and low magnetic permeability above a predetermined Curie point temperature, a pair of movable contacts carried by the armature and adapted to engage the pair of stationary contacts for connecting the armature in series with the electric circuit to be protected to heat the armature in accordance with the current ow in said electric circuit, a permanent magnet acting upon the armature between the movable contacts in a direction to hold the movable contacts in engagement with the stationary contacts when the temperature of the armature is below the Curie point temperature, and spring means acting upon the armature between the movable contacts in the opposite direction to disengage the movable contacts from the stationary contacts when the temperature of the armature rises to substantially the Curie point temperature due to a sustained low current overload condition in the electric circuit to be protected for opening said circuit, and a pair of cores having high magnetic permeability carried by the armature and extending into the central openings of the pair of coils for moving the armature in the opposite direction to disengage the pair of movable contacts from the pair of stationary contacts when the current flow in the coils exceeds a predetermined value due to a sudden high current overload condition in the electric circuit to be protected for opening the circuit.

13. An overload circuit breaker for protecting an electric circuit against current overload conditions therein comprising, high current coil means, contact means and an armature connected in series in the electric circuit to be protected, said armature actuating the Contact means and having resistance to current ow so as to be heated by current ow therethrough and high magnetic permeability below and low magnetic permeability above a predetermined Curie point temperature, a permanent magnet magnetically coupled to the armature and acting upon the armature in a direction to hold the contact means closed when the temperature of the armature is below the Curie point temperature, spring means acting upon the armature in a direction to uncouple the armature and open the contact means when the temperature of the armature rises to substantially the Curie point temperasure due to a sustained low current overload condition in the electric circuit to be protected for opening said nagegaan? circuit, and core means having high magnetic permeability carried by the armature and associated with the coil means for moving the armature in said opposite direction to uncouple the armature from the permanent magnet and'open the contact means when the current ow in the coil means exceeds a predetermined value due to a sudden high current overload condition in the electric cirtact means and an armature connected in series in the electric circuit to be protected, said armature actuating the contact means and having resistance to current flow so vas to be heated by current flow therethrough and high magnetic permeability below and low Y magnetic permeability above a predetermined Curie point temperature, a permanent magnet magnetically coupled to the armature and acting upon the armature in a direction tohold thecontact means closed when. the temperature of the armature is below the Curie point temperature, sering means acting upon the armature in a direction to uncouple the'arrnature and open the contact means when the temperature of the armature rises to substantially the Curie point temperature due to a sustained low current overload condition in the electric circuit to bel protected for opening'said circuit, and core` means having high-4 magnetic permeability carried by the armature and asso-- ciated with the coil means for moving the armatureinf saidopposite Adirection to uncouple the armature from the permanent magnet and open the contact means whenvv the-current ow in the coil means exceeds a predeter-` mined value due to a sudden high current overload condition in the electric circuit to be protected for opening said circuit, and means for manually moving the per# marient magnet to magnetically recouple lthe armature" to the magnet after the armature has been moved by the j,

spring means or the coil means to open thel contact means for the purpose of reclosing the contact means and resetting the circuit breaker.

References tlited in the tile of this patent UNITED STATES PATENTS 1,122,359 France May 22', 1956 Frohne Mar. 30, 1926 

